public static WherePart Concat(WherePart left, string @operator, WherePart right)
{
return(new WherePart()
{
Parameters = left.Parameters.Union(right.Parameters).ToDictionary(kvp => kvp.Key, kvp => kvp.Value),
Sql = $"({left.Sql} {@operator} {right.Sql})"
});
}
public static WherePart Concat(string @operator, WherePart operand)
{
return(new WherePart()
{
Parameters = operand.Parameters,
Sql = $"({@operator} {operand.Sql})"
});
}
public static WherePart Recurse(ref int i, Expression expression, bool isUnary = false, string prefix = null, string postfix = null)
{
//source: http://ryanohs.com/2016/04/generating-sql-from-expression-trees-part-2/
if (expression is UnaryExpression unary)
{
return(WherePart.Concat(NodeTypeToString(unary.NodeType), Recurse(ref i, unary.Operand, true)));
}
if (expression is BinaryExpression body)
{
return(WherePart.Concat(Recurse(ref i, body.Left), NodeTypeToString(body.NodeType), Recurse(ref i, body.Right)));
}
if (expression is ConstantExpression constant)
{
var value = constant.Value;
if (value is int)
{
return(WherePart.IsSql(value.ToString()));
}
if (value is string)
{
value = prefix + (string)value + postfix;
}
if (value is bool && isUnary)
{
return(WherePart.Concat(WherePart.IsParameter(i++, value), "=", WherePart.IsSql("1")));
}
return(WherePart.IsParameter(i++, value));
}
if (expression is MemberExpression member)
{
if (member.Member is PropertyInfo property)
{
var colName = property.Name;
if (isUnary && member.Type == typeof(bool))
{
return(WherePart.Concat(Recurse(ref i, expression), "=", WherePart.IsParameter(i++, true)));
}
return(WherePart.IsSql("[" + colName + "]"));
}
if (member.Member is FieldInfo)
{
var value = GetValue(member);
if (value is string)
{
value = prefix + (string)value + postfix;
}
return(WherePart.IsParameter(i++, value));
}
throw new Exception($"Expression does not refer to a property or field: {expression}");
}
if (expression is MethodCallExpression methodCall)
{
// LIKE queries:
if (methodCall.Method == typeof(string).GetMethod("Contains", new[] { typeof(string) }))
{
return(WherePart.Concat(Recurse(ref i, methodCall.Object), "LIKE", Recurse(ref i, methodCall.Arguments[0], prefix: "%", postfix: "%")));
}
if (methodCall.Method == typeof(string).GetMethod("StartsWith", new[] { typeof(string) }))
{
return(WherePart.Concat(Recurse(ref i, methodCall.Object), "LIKE", Recurse(ref i, methodCall.Arguments[0], postfix: "%")));
}
if (methodCall.Method == typeof(string).GetMethod("EndsWith", new[] { typeof(string) }))
{
return(WherePart.Concat(Recurse(ref i, methodCall.Object), "LIKE", Recurse(ref i, methodCall.Arguments[0], prefix: "%")));
}
// IN queries:
if (methodCall.Method.Name == "Contains")
{
Expression collection;
Expression property;
if (methodCall.Method.IsDefined(typeof(ExtensionAttribute)) && methodCall.Arguments.Count == 2)
{
collection = methodCall.Arguments[0];
property = methodCall.Arguments[1];
}
else if (!methodCall.Method.IsDefined(typeof(ExtensionAttribute)) && methodCall.Arguments.Count == 1)
{
collection = methodCall.Object;
property = methodCall.Arguments[0];
}
else
{
throw new Exception("Unsupported method call: " + methodCall.Method.Name);
}
var values = (IEnumerable)GetValue(collection);
return(WherePart.Concat(Recurse(ref i, property), "IN", WherePart.IsCollection(ref i, values)));
}
//Everything else - like datetime.now
var val = Expression.Lambda(methodCall).Compile().DynamicInvoke();
return(WherePart.IsParameter(i++, val));
}
throw new Exception("Unsupported expression: " + expression.GetType().Name);
}